Re: bipedalism and AAH
Pat Dooley (patdooley@aol.com)
8 May 1995 22:09:14 -0400
Nicholls writes :
<< deletions >>
> That is, the studies which I have cited repeatedly disproves
>the assumption that bipedalism is less efficient that quadrupedalism at
>least when it comes to walking. The measurments were taken on
chimpanzees
>because they are living and it is somewhat difficult to take these
>readings on fossils.
Energy efficient or survival efficient?
Is an ape going through the process
of radically altering its pelvic structure, the length of its legs, its
internal
anatomy, the shape of its spine, the position of its skull, and all the
other
structural changes associated with true bipedalism, going to be as
efficient at
bipedalism as quadrupedalism during that process?
At various points during that process, both quadrupedal and bipedal
efficiency are going to be reduced to the point where neither is as
good as the starting point - 100% quadrupedalism or the end-point - 100%
bipedalism, either in energy efficient terms or surival efficiency terms.
Evolution doesn't give you a sub-optimal holiday while you evolve an
optimal solution - the principle of non-disadvantageous intermediates.
>My point is that the common ancestor was not a knuckle-walker as has
>been fairly well demonstrated, that it was most likely an arboreal
>ape (clearly indicated by Lucy's limb bone proportions and curved
>toes) and very likely a suspensory feeder. The latter adapation
>would predispose it to be a biped when it moved on the round, much
>the same as gibbons and spider monkeys who are modern suspensory
>feeders. This is not to imply that humans are descended from either
>spider monkeys or gibbons.
Your spider monkeys or gibbons are a red herring.
I think you are putting yourself out on a limb by claiming Lucy was
a suspensory feeder. There is no earthly reason why such a
suspensory feeder should become bipedal in the human sense.
(Standing or walking on two legs for short periods does not
qualify as bipedalism, despite what some posters claim.)
Pat D
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